The present invention is directed, in general, to frame relay and ATM communications and, more specifically, to an ATM switch containing a frame relay proxy signaling agent that allows frame relay end users to communicate across an ATM network.
Information systems have evolved from centralized mainframe computer systems supporting a large number of users to distributed computer systems based on local area network (LAN) architectures. As the cost-to-processing-power ratios for desktop PCs and network servers have dropped precipitously, LAN systems have proved to be highly cost effective. As a result, the number of LANs and LAN-based applications has exploded. A consequential development relating to the increased popularity of LANs has been the interconnection of remote LANs, computers, and other equipment into wide area networks (WANs) in order to make more resources available to users. However, a LAN backbone can transmit data between users at high bandwidth rates for only relatively short distances. In order to interconnect devices across large distances, different communication protocols have been developed. These include X.25, ISDN, and frame relay, among others.
Most data transmissions, including file transfers and voice, occur in bursts at random intervals. The bursty nature of most data transmissions means that if the bandwidth allocated to a transmitting device is determined according to its peak demand, much bandwidth is wasted during the xe2x80x9csilencesxe2x80x9d between data bursts. This variable bandwidth demand problem has been solved in part by X.25 and frame relay,: which use statistical multiplexing to improve the throughput of multiple users. Statistical multiplexing takes advantage of the bursty nature of data transmissions to allow a user to transmit bursts of data in excess of the user""s allocated bandwidth for relatively short periods of time.
Frame relay has proved to be a popular communication protocol. Frame relay provides up to T3 level speeds (from 56 Kbps up to about 45 Mbps) using packet switching technology. It is optimized for the transfer of protocol-oriented data in packets of variable length. Data is sent in high-level data link control packets, called xe2x80x9cframesxe2x80x9d. A typical frame includes a xe2x80x9cheaderxe2x80x9d, comprising an address block and a control block, a xe2x80x9cpayloadxe2x80x9d or data block that is the actual data to be transferred from endpoint to endpoint, and a CRC error correction block.
An end user transmits data according to a committed information rate (CIR) and a maximum burst size. Bandwidth is allocated dynamically on a packet-by-packet basis within the network. If the end user exceeds the CIR for a short period of time, the transmitted data is buffered within the frame relay network for later transmission. If this condition persists, however, traffic policing and congestion control mechanisms in the network reduce the rate at which the end user transmits data.
Frame relay frames have only a small amount of xe2x80x9coverheadxe2x80x9d (i.e., header and CRC), only seven (7) bytes compared to hundreds of data bytes). However, the variable lengths of the payload cause variable length delays as the frames move through the network switches. This makes frame relay suitable to pure data transfers, but less suitable to the transfer of mixed voice, data and video. Additionally, the newest LAN/WAN applications, including file transfers, imaging, video conferencing, and the like, demand great amounts of bandwidth that cannot be serviced by frame relay.
ATM is a relatively new technology and currently represents only a comparatively small percentage of the installed network infrastructure. Frame relay still remains as a dominant portion of the installed network infrastructure. Additionally, since many information systems may never need video or other high bandwidth applications, it is unlikely that every LAN or WAN system will need to be converted to an ATM system. Hence, frame relay and ATM will likely coexist for a long period of time.
In order to allow frame relay systems and ATM systems to communicate with one another, a host of well-known interfaces have been developed to interconnect frame relay based networks with ATM based networks. These frame relay-to-ATM interfaces typically include a high-level data link control (HDLC) interface for sending and receiving frames from a frame relay-based network and a segmentation and reassembly (SAR) interface for sending and receiving cells from an ATM-based network. Between the HDLC and the SAR, a memory holds the payloads of the frames and/or cells, and a traffic control processor monitors the traffic for every connection and adjusts the traffic flow based on a leaky bucket software routine. The traffic control processor also provides the frame switching and forwarding functions for every connection.
It is therefore common to find networks containing a mixture of interconnected frame relay devices and ATM devices communicating with one another via an ATM backbone network. To increase the effective throughput of the backbone ATM network, devices called concentrators are frequently used to receive frame relay frames and ATM cells from a group of ATM devices and frame relay devices. A concentrator convert all of the mixed-input traffic to ATM cells on it output and combines and compacts the output traffic before it reaches the high capacity ATM network.
A problem occurs if two frame relay devices attempt to communicate via an ATM network. Many of the nodes in an ATM network, such as concentrators do not contain the signaling support devices needed to establish dynamic connections between two frame relay devices. The concentrators are relatively simple devices that are not easily modified to provide the necessary signaling support to allow communication between two frame relay devices across an ATM network.
There is therefore a need in the art for an improved ATM network that allows a first frame relay device to communicate with a second frame relay device without either frame relay device being directly connected to a device that facilitates dynamic connections of frame relay devices. In particular, there is a need for an improved ATM switch capable of supporting frame switching and signaling.
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide,for use in an ATM network capable of transporting data between a first node and a second node operable to transmit and receive frame relay data frames, wherein the first node is coupled to an ATM access device incapable of providing to the first node support for switched virtual circuit (SVC) connections, a system for servicing an SVC connection between the first node and the second node. In one embodiment of the present invention, the system comprises: 1) a connection controller capable of establishing a fixed connection between the ATM access device and a selected intermediate node in the ATM network; and 2) a frame relay proxy controller disposed at the selected intermediate node and adapted for communicating via the fixed connection established by the connection controller, wherein the frame relay proxy controller receives SVC signaling information from the first node via the fixed connection and establishes an SVC connection with the second node.
In one embodiment of the present invention, the intermediate node is an ATM switch.
In another embodiment of the present invention, the fixed connection is a permanent virtual circuit (PVC) connection.
In still another embodiment of the present invention, the connection controller is a network management system.
In a further embodiment of the present invention, the ATM access device is an ATM access concentrator capable of receiving a plurality of input data streams and merging the plurality of input data streams into an ATM cell output stream having a data rate higher than at least one of the plurality of input data streams.
In yet another embodiment of the present, invention, at least one of the input data streams comprises frame relay data frames received from a frame relay device.
In a still further embodiment of the present invention, at least one of the input data streams comprises ATM cells received from an ATM device.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking, the DETAILED DESCRIPTION, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprise,xe2x80x9d as well as derivatives thereof, mean inclusion without limitation; the term xe2x80x9cor,xe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewith,xe2x80x9d as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or, the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for, certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.